1. Field of the Invention
The present invention relates generally to a compressor which reciprocates pistons by rotating a wave cam provided integrally with a drive shaft. More particularly, it pertains to a wave cam and its manufacturing method.
2. Description of the Related Art
In compressors that reciprocate pistons by rotating a swash plate, each piston is reciprocated once for every rotation of the plate. Hence, it is necessary to enlarge the size of the compressor to increase the compressing displacement per rotation of the swash plate.
To cope with this problem, a wave cam compressor has been recently proposed. This compressor employs a three-dimensional, convex, wave-shaped cam in lieu of the swash plate.
A wave cam type compressor, such as the type disclosed in Japanese Unexamined Patent Publication 57-110783 displaces double-headed pistons by way of rollers. This reciprocates the double-head pistons according to a displacement curve defined by the surface of the wave cam.
However, the wave cam disclosed in the above publication employs a cam surface having continuous concave and convex surfaces. Grinding conditions differ between the concave and convex surfaces. This not only results in troublesome machining but also lowers accuracy, especially at the boundary portions between the concave and convex surfaces. Thus, this may lead to the cam surface having inconsistent surface roughness and dimensions. Dimensional inaccuracy at these boundaries may have effects on the movement of the pistons and cause a decrease in the efficiency of the compressor.